The present invention relates to an apparatus for high speed stacking of paper sheets or forms. The stacking is provided by the apparatus according to the invention by either accordion-like folding of a continuous web along preset spaced portions thereof or, alternatively, by a simple superimposition of separated sheets.
Such an apparatus is particularly useful both in preparing paper for high speed printers, such as laser printers or the like, as a continuous accordion folded web to provide packages containing a preset number of loops or "forms" connected to each other by transversal prepierced lines, and in the superimposition of said forms coming out from the printer, after they each have been separated from each other by a tear action along the above mentioned prepierced lines.
More specifically, the present invention pertains to the apparatus to effect a tear separation along prepiercing lines preset in the continuous web and defining the single forms or sheets.
Devices for providing this tear separation are already known, and as an example, it is possible to mention the device covered by the utility model Italian patent No. 215262 filed on Nov. 21, 1988.
Devices advantageously solving the problem of providing a continuous accordion-like folded web are already know, as for example those which were the subject matter of the Italian patent applications S. N. 22536 A/88 filed on Nov. 7, 1988 (granted as U.S. Pat. No. 1,227,467) and S. N. 21466 A/89 filed on Aug. 7, 1989 in the name of the present applicant to which reference will be made in the description of the device according to the present invention.
It has been noticed that the devices of the above applications and patents, although are completely reliable for doing the duty entrusted to them, while there were some working problems for what is regarded as the tear separation and the means provided to direct the continuous web portions to one or the other of the stopping and/or fending stations of the end edges of said portions.
Further it has been noticed that the versatility of said devices was limited by the fact that they hardly could be used for stacking loose forms i.e. forms coming out from the printer as a continuous web and separated from each other, for example, by tear separation.
The stacking of the forms separated from each other is not certainly an operation which can be carried out easily because, differently from the continuous web for which there are no specific problems in directing the portions thereof to the stopping and/or folding stations, as the above mentioned web is a continuous piece, said problems are relevant in the case of separated forms either in driving or suitably directing them. It is an object of the present invention to provide an apparatus which can solve the above mentioned problems in an advantageous, simple and reliable way.
It is a more specific object of the present invention to provide a tear separating device useful in a device of the above mentioned kind.
The main object of the present invention is met by a high speed stacking apparatus of resilient material sheets or forms for either an accordion-like folding of a continuous web or a superimposition of seperated sheets each of which is fed by a continuous web and comprises driving means thereof to diverting means of either properly spaced portions thereof or of the leading edge of said sheets to a first or second stopping and/or folding station arranged on two opposed sides of the stacking plane of the sheets, characterized in that between the inlet area of the web to the apparatus and said diverting means are provided directing means of the web associated with driving means and with actuatable means to provide the tear separation of said web along a transversal pierced line, the above mentioned diverting means comprising nozzle means connected to a compressed air source, said nozzle means being able to provide an air blow directed substantially perpendicularly with respect to the paper sheet coming out from the said directing means and downstream with respect to said tear separating means.
In turn, the tear separating device according to the invention in its most general embodiment comprises:
a first cylindrical roller pair facing each other faced and in frictional contact with said sheet, every roller rotating around its own axis at a constant peripheral speed and in contrary directions for driving the paper web along a preset path;
a second cylindrical roller pair, everyone of them being provided with a planar bevel, said bevels facing each other and being spaced with respect to said sheet and having a substantially equal extension, said second pair being arranged downstream with respect to said first pair;
the rollers of said second pair being rotatable on command around their own axes and in contrary directions to carry out at least a complete turn with peripheral speed higher than that of said first pair, said rollers getting in frictional contact with said paper web, in which at least a roller of said second pair comprises a series of cylinders spaced from each and aligned along their axes and said cylinder series comprising at least a central cylinder and lateral cylinders, the central cylinders being staggered in an advanced phase with respect to the lateral cylinders, so that said central cylinders get early in frictional touch with said sheet with respect to the lateral cylinders.
According to another embodiment which is variation of the tear separation device useful in the apparatus according to the invention, the rollers of the first pair are also provided with the bevels or millings above defined for said second roller pair, without having the already mentioned phase staggering feature of the central cylinders with respect to the lateral ones.
According to another preferred embodiment of this variation, the rollers of the second roller pair have a cross-section larger than that of said first pair.
According to a further embodiment of this variation the upstream arranged pair of friction advancement rollers of the paper web is omitted and the rollers of said first pair are moved by a continuous rotation movement.